In recent years, for example, liquid crystal display devices are widely used in liquid crystal television sets, monitors, mobile phones and the like as flat panel displays that are thinner and lighter in weight than the existing cathode ray tube displays. Such a liquid crystal display device includes: an illumination device (backlight device) that emits light; and a liquid crystal panel that includes a liquid crystal layer including liquid crystal molecules and a pair of substrates sandwiching the liquid crystal layer and that functions as a shutter with respect to light emitted from a light source provided in the illumination device and displays an intended image.
The liquid crystal display device as described above is known to have a control system such as, for example, a twisted nematic (TN) mode in which vertical electric fields are applied to the liquid crystal layer so as to control the alignment of the liquid crystal molecules contained in the liquid crystal layer, an in-plane switching (IPS) mode in which horizontal electric fields are applied to the liquid crystal layer so as to control the alignment of the liquid crystal molecules contained in the liquid crystal layer, or an FFS mode. In particular, more attention is paid to the FFS mode liquid crystal display device that has better viewing angle characteristics than a vertical electric field liquid crystal display device such as the TN mode liquid crystal display device and has a higher light transmittance than the IPS mode liquid crystal display device.
To be specific, as the conventional liquid crystal display device described above, Patent Document 1 listed below discloses a liquid crystal display device in which on an active matrix substrate (one of a pair of substrates) side on which a thin film transistor (TFT) that serves as a switching element is provided for each pixel, a pixel electrode that is connected to the thin film transistor is provided. Also, in the conventional liquid crystal display device, on the active matrix substrate side, a flat plate-like common electrode is provided so as to oppose the pixel electrode having comb-tooth portions, with an interlayer insulating layer interposed therebetween. The common electrode and the pixel electrode are made of a transparent electrode material. The common electrode is connected to a common interconnect line. In the conventional liquid crystal display device, based on a switching operation of the thin film transistor, fringing electric fields are formed between the common electrode and the pixel electrode so as to pass through the comb-tooth portions, and the alignment of the liquid crystal molecules contained in the liquid crystal layer is controlled by the fringing electric fields, and an image is thereby displayed.